How to differentiate maternal from fetal heart rate patterns on electronic fetal monitoring
Three cases illustrate how maternal heart rate may masquerade as a fetal heart rate pattern and obscure the interpretation of EFM recordings
CASE 3 Low fetal heart rate and variability during contractions
A 22-year-old woman (G2P1) in spontaneous labor at term progressed to complete dilation. Fetal heart rate accelerations occurred for approximately 30 minutes. With the advent of pushing, the fetal heart rate showed a rate of 130 to 140 BPM and mild decelerations with each contraction (FIGURE 4A). As the second stage progressed, the tracing demonstrated an undulating baseline heart rate between 100 and 130 BPM with possible variability during contractions (FIGURE 4B). This pattern continued for an additional 60 minutes. At vaginal delivery, the ObGyn was surprised to deliver a depressed newborn with Apgar scores of 1 and 3 at 1 and 5 minutes, respectively.
Slipping from the fetal to the maternal heart rate may be imperceptible
In contrast to the breaks in the tracings seen in Case 1 and Case 2, the EFM tracing in Case 3 appears continuous. Yet, slipping from the fetal to the maternal recording was occurring.
,As seen in FIGURE 4C, the maternal heart rate with variability was recorded during pushing efforts, and the fetal heart rate was seen rising back toward a baseline between contractions. Note that the fetal heart rate did not reach a level baseline, but rather decelerated with the next contraction. The slipping to the maternal heart rate occurred without a perceptible break in the recording, making this tracing extremely difficult to interpret.
CASE 3 Be ever vigilant
The lack of recognition that the EFM recording had slipped to the maternal heart rate resulted in fetal and newborn hypoxia and acidosis, accounting for the infant’s low Apgar scores.
Read how using 3 steps can help you distinguish fetal from maternal heart rate patterns
